feat(monitoring): add Redis exporter + Sentry docs to deployment guide

- Add redis-exporter container to docker-compose (oliver006/redis_exporter, 32MB)
- Add Redis scrape target to Prometheus config
- Add 4 Redis alert rules: RedisDown, HighMemory, HighConnections, RejectedConnections
- Document Step 19b (Sentry Error Tracking) in Hetzner deployment guide
- Document Step 19c (Redis Monitoring) in Hetzner deployment guide
- Update resource budget and port reference tables

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/development/frontend-exception-handling.md

@@ -49,7 +49,7 @@ apiClient.interceptors.response.use(
       };
       throw apiError;
     }
-    
+
     // Handle network errors
     if (error.code === 'ECONNABORTED') {
       throw {
@@ -58,7 +58,7 @@ apiClient.interceptors.response.use(
         statusCode: 408
       };
     }
-    
+
     throw {
       errorCode: 'NETWORK_ERROR',
       message: 'Network error. Please check your connection.',
@@ -105,7 +105,7 @@ class ApiClient {
       if (error.errorCode) {
         throw error; // Re-throw API errors
       }
-      
+
       // Handle network errors
       throw {
         errorCode: 'NETWORK_ERROR',
@@ -130,28 +130,28 @@ export const ERROR_MESSAGES = {
   INVALID_CREDENTIALS: 'Invalid username or password. Please try again.',
   TOKEN_EXPIRED: 'Your session has expired. Please log in again.',
   USER_NOT_ACTIVE: 'Your account has been deactivated. Contact support.',
-  
+
   // MarketplaceProduct errors
   PRODUCT_NOT_FOUND: 'MarketplaceProduct not found. It may have been removed.',
   PRODUCT_ALREADY_EXISTS: 'A product with this ID already exists.',
   INVALID_PRODUCT_DATA: 'Please check the product information and try again.',
-  
+
   // Inventory errors
   INSUFFICIENT_INVENTORY: 'Not enough inventory available for this operation.',
   INVENTORY_NOT_FOUND: 'No inventory information found for this product.',
   NEGATIVE_INVENTORY_NOT_ALLOWED: 'Inventory quantity cannot be negative.',
-  
+
   // Shop errors
   SHOP_NOT_FOUND: 'Shop not found or no longer available.',
   UNAUTHORIZED_SHOP_ACCESS: 'You do not have permission to access this shop.',
   SHOP_ALREADY_EXISTS: 'A shop with this code already exists.',
   MAX_SHOPS_REACHED: 'You have reached the maximum number of shops allowed.',
-  
+
   // Import errors
   IMPORT_JOB_NOT_FOUND: 'Import job not found.',
   IMPORT_JOB_CANNOT_BE_CANCELLED: 'This import job cannot be cancelled at this time.',
   MARKETPLACE_CONNECTION_FAILED: 'Failed to connect to marketplace. Please try again.',
-  
+
   // Generic fallbacks
   VALIDATION_ERROR: 'Please check your input and try again.',
   NETWORK_ERROR: 'Connection error. Please check your internet connection.',
@@ -179,7 +179,7 @@ export const useApiError = () => {
   const handleApiCall = async (apiCall) => {
     setIsLoading(true);
     setError(null);
-    
+
     try {
       const result = await apiCall();
       setIsLoading(false);
@@ -233,7 +233,7 @@ const ProductForm = () => {
       if (apiError.field) {
         setFieldErrors({ [apiError.field]: apiError.message });
       }
-      
+
       // Handle specific error codes
       switch (apiError.errorCode) {
         case 'PRODUCT_ALREADY_EXISTS':
@@ -312,7 +312,7 @@ class ErrorBoundary extends React.Component {
 
   componentDidCatch(error, errorInfo) {
     console.error('Error caught by boundary:', error, errorInfo);
-    
+
     // Log to error reporting service
     if (window.errorReporting) {
       window.errorReporting.captureException(error, {
@@ -442,7 +442,7 @@ const handleInventoryUpdate = async (gtin, location, quantity) => {
     switch (error.errorCode) {
       case 'INSUFFICIENT_INVENTORY':
         const { available_quantity, requested_quantity } = error.details;
-        notificationManager.notify('error', 
+        notificationManager.notify('error',
           `Cannot remove ${requested_quantity} items. Only ${available_quantity} available.`
         );
         break;
@@ -493,7 +493,7 @@ const ImportJobStatus = ({ jobId }) => {
       switch (error.errorCode) {
         case 'IMPORT_JOB_CANNOT_BE_CANCELLED':
           const { current_status } = error.details;
-          notificationManager.notify('error', 
+          notificationManager.notify('error',
             `Cannot cancel job in ${current_status} status`
           );
           break;
@@ -549,12 +549,12 @@ export const logError = (error, context = {}) => {
   try {
     const existingErrors = JSON.parse(localStorage.getItem('apiErrors') || '[]');
     existingErrors.push(errorData);
-    
+
     // Keep only last 50 errors
     if (existingErrors.length > 50) {
       existingErrors.splice(0, existingErrors.length - 50);
     }
-    
+
     localStorage.setItem('apiErrors', JSON.stringify(existingErrors));
   } catch (e) {
     console.warn('Failed to store error locally:', e);